This invention relates generally to the production of kinescopes for color television receivers and particularly to a fixture for accurately aligning the sealing edges of the panel and funnel of such kinescopes prior to fritting the panel and funnel together.
A kinescope for a color television receiver produces a visual display by scanning three electron beams across a phosphor screen which emits light upon impact by electrons. The phosphor screen is arranged on the inside surface of a faceplate panel and is composed of triads of phosphors which produce the three different colors of light when scanned with electron beams. The electron beams are provided by electron guns which are supported in a cylindrical neck. The neck is attached to a funnel-shaped portion by a contoured portion. The electron beams are directed toward the screen and are deflected horizontally and vertically by a magnetic yoke which is arranged at the contoured portion of the funnel. A shadow mask is arranged between the electron guns and the phosphor screen and the three electron beams are converged at the shadow mask. The shadow mask contains a large plurality of apertures through which the electron beams pass prior to impacting the phosphor screen. The shadow maks serves as a color-section electrode to cause each of the three electron beams to impact a phosphor of a proper color.
After the phosphor screen is produced on the inside surface of the faceplate panel, and the shadow mask is inserted it is necessary to permanently affix the faceplate panel to the funnel. This is accomplished by providing both the faceplate panel and the funnel with mating sealing edges. A frit material is placed on the sealing edge of one of the elements and the elements are then placed in a fixture which aligns the two elements. The fixture along with the funnel and faceplate panel are then passed through an oven which solidifies the frit material to permanently and hermetically join the panel and the funnel.
Because during the operation of the kinescope, it is necessary for a particular electron beam to impact a phosphor which emits a particular color of light, it is essential that the faceplate panel and funnel be accurately aligned prior to permanently joining the two elements. In the prior art, the fixture which supports the funnel and the panel during fritting has been provided with referencing pins which are intended to accurately align the sealing edges of the funnel and the panel. However, problems frequently arise because the referencing pins sometimes wear or are broken resulting in unacceptable alignment. Additionally, with the prior art devices, loading of the components onto the fixtures is done manually so that the individual placing the funnels and panels into the fixture can attempt to verify that the elements properly contact the referencing members. Manual leading also is required; because the funnel slides along the reference pins. The friction between the funnel glass and pins is high and it, therefore, is possible for a funnel to be inaccurately positioned in the fixture and thus fail to contact all the reference pins. The present trend toward the automation of production results in a need for a fixture which will permit the automatic loading of the funnels and panels onto the sealing fixture while simultaneously assuring the accurate alignment of the elements without the need for manual verification. There also is a need for a fixture which minimizes the friction between the funnel and the fixture so that gravity can be relied on to accurately position the funnel in the fixture. The instant invention fulfills this need by the provision of a sealing fixture for color kinescopes in which all contact with the kinescope funnel and the fixture is accomplished through rotatable referencing elements to thereby minimize wear of the referencing members and also to minimize friction between the funnel and the fixture to assure that gravity accurately positions the funnel in the fixture.